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-1
votes
3answers
96 views

Gravity effects when deleting stars or planets

In one of the latest SCIFI movies, they collect a star absorving it entirely in a kind of planet size gun/machine. As mass cannot disappear, I assume it was just concentrated inside their machine (...
1
vote
0answers
54 views

On the Stability of Circular Orbits

Bertrand's Theorem characterizes the force laws that govern stable circular orbits. It states that the only force laws permissible are the Hooke's Potential and Inverse Square Law. The proof of the ...
0
votes
0answers
17 views

How can I measure the stability of a many body gravitational system?

Suppose I have an N body planetary system interacting via gravity. Suppose I know the positions and momenta at t=0. How do I know if this system is stable (indefinitely)? By stable I mean the ...
0
votes
0answers
31 views

Heliocentric Cartesian position of moons

I have a working Kepler orbit system that is GPU accelerated to allow precision, speed and parallelism and more importantly allow as many factors as possible in calculation. For various reasons I ...
1
vote
1answer
50 views

Stability of the classical helium atom

Let us forget about quantum mechanics and confine ourselves to classical mechanics. The Hamiltonian for a classical helium atom would be $$ H = \frac{p_1^2 + p_2^2}{2m } - \frac{Z}{r_1} - \frac{Z}{...
-3
votes
4answers
105 views

Orbits for dummies [duplicate]

In a certain universe a perfectly spherical, uniformly dense planet is found to be in a stable orbit around a stable star. The rest of the universe is empty space with no silly stuff like dark matter. ...
1
vote
1answer
24 views

Would a celestial body in a horseshoe orbit be tidally locked to the planet?

A smaller celestial body like a moon or an asteroid can be in a horseshoe orbit around a planet. Since it might go inside the tidal lock radius (but does not stay inside it all the time), during the ...
1
vote
1answer
308 views

Determing Velocity of Moons

I have a question that I believe is relatively easy to answer, I am working on an $N$-body simulation of a fictional star system and am having trouble finding the velocity of moons so that they will ...
1
vote
2answers
67 views

Which timestep should I use for a $N$-body simulation of the Solar system?

I am trying to implement a $N$-body simulation of the Solar system and I am stuck on the issue of the simulation timestep size. At first I would like to use a simple Euler stepping scheme. Knowing ...
2
votes
3answers
351 views

What would Earth have been without the Moon?

Would Earth rotation have been more slowed down because of the tidal effect from the Sun, as seems to be the case with Mercury and Venus? Due to the giant impact hypothesis the angular momentum from ...
1
vote
2answers
43 views

Reference frame, gravitation and kinetic energy

English is not my primary language. I apologize (and would like corrections) if the terms I use are not the right ones. In a geocentric reference frame, the moon rotates around the Earth. So its ...
0
votes
1answer
73 views

As planets orbit around the Sun, does the force of gravity due to the Sun remain constant?

I know that the force of gravity is: $$F = GMm/R^2$$ Where $G$ is gravitational constant, $M$ is mass of sun, $m$ is mass of the orbiting planet and $R$ is the distance between the center of their ...
3
votes
2answers
101 views

What is the zero of potential?

A satellite of mass $m$ is travelling at a speed $v_0$ in a circular orbit of radius $r_0$ around a fixed mass at $O$. Taking the zero of potential at $r=\infty$, show that the total energy of the ...
0
votes
3answers
83 views

Gravitational acceleration of asteroids [closed]

If an asteroid is moving through space at a speed that exceeds escape velocity of the earth and that asteroid is on a collision course with the earth will the asteroid Accelerate as it falls into the ...
16
votes
8answers
4k views

Why doesn't orbital body keep going faster and faster? [duplicate]

If we consider the change in velocity during an infinitesimal interval of an orbit: where body B is orbiting body A, we can see that the magnitude of the resultant vector (the green arrow) is ...
1
vote
2answers
317 views

Why Sun is not able to attract mercury closer?

As sun have a huge amount of attraction pull force , why its not able to pull tiny mercury? Is the whole solar system works in a push and pull network? Why bigger planets like earth, Saturn and ...
1
vote
2answers
57 views

What does “transfer” of angular momentum mean?

The Moon’s gravity produces tidal deformations or “bulges” in the Earth. Because of the Earth’s rotation, the line that goes through the bulges is not aligned with the line between the Earth and the ...
0
votes
0answers
27 views

Keplerian orbits and radial velocities: problem with true anomalies

I am writing a pure Python code to calculate radial velocities of stars with massive objects orbiting them. I am following the formalism from Murray & Correia (2011) (hereafter MC11). In a given ...
4
votes
1answer
22 views

How would I find the velocity of an object after it doesn't fully enter the gravitational pull of a planet and is kind sling shot out of its gravity?

Obviously that question doesn't have a lot of jargon having to do with math and physics. I am not a physicist, I'm not a mathematician, I'm trying to make a game and simulate some physics found in ...
0
votes
1answer
30 views

Earth, Sun and beginner's reference frames

In the post-Newton era, where "absolute space" is not absolute, how is the reference frame in which "the Earth moves round the Sun" accurately defined?
1
vote
1answer
43 views

Energy diagram of a planet with fixed mechanical energy

Consider the following energy diagram for the motion of a planet about a star. The centrifugal potential curve can be represented once I fixed the angular momentum $\vec{L}$ of the planet. To fix the ...
0
votes
0answers
59 views

Celestial bodies trajectories relative to each other and with respect to the CM

In a two bodies $A$ and $B$ system, both under the action of an internal force of interaction $\vec{F}$, the motion of $A$ as seen from $B$, is equivalent to the motion of a single body of mass $\mu=\...
5
votes
1answer
66 views

Methods for handling close approaches in $N$-body simulations

In direct gravitational $N$-body simulations, what are the preferred methods for handling close approaches between bodies in order to preserve the accuracy of the evolution of the system?
1
vote
0answers
29 views

Can a satellite be put into orbit such that it will always remain directly over a city? [duplicate]

Isn't it possible if we just set it high enough so that it's angular speed matches with the earth's? I think that the city must be on the equator to make this happen. Am I correct? Please can anyone ...
0
votes
1answer
80 views

Can a satellite remain directly over a city?

Is it possible to put an artificial satellite into an orbit in such a way that it will always remain direct over a city (I mean at any specific place)?
7
votes
3answers
534 views

How to learn celestial mechanics?

I'm a PhD student in math and am really excited about celestial mechanics. I was wondering if anyone could give me a roadmap for learning this subject. The amount of information about it on the ...
0
votes
0answers
21 views

Books on Celestial Mechanics [duplicate]

My background is mathematics. I would like to study celestial (not classical) mechanics and looking for an appropriate book. I found that somebody has already asked a similar question "How to learn ...
0
votes
0answers
19 views

Journals which publish articles on Celestial Mehanics [duplicate]

I'm from mathematics and want to study celestial mechanics further. In order to know literature at research level, I would like to know in which journals we can find papers on celestial mechanics. The ...
1
vote
0answers
16 views

Research groups in celestial mechanics [closed]

This Exchange may not be the right place to to ask this question, but I would like to know prominent research groups working in celestial mechanics. Although I'm interested in celestial mechanics, ...
0
votes
0answers
60 views

How to visualize gravity fields? [closed]

I'm creating a tool for intuitively prototyping routes through space. Part of this requires visualizing gravity. This is the formula for working at how much gravity is at a particular location: <...
0
votes
1answer
76 views

Newtonian Gravity Simulator?

Could anyone suggest me a good (and possibly free) Newtonian Gravity Simulator software available on the web, where it might be possible to simulate the Solar System dynamics and playing with it, by ...
2
votes
2answers
295 views

Planetary alignment of the gas giants?

There is this nice and new applet of the orbits of the planets around the sun: Solar System Orrery You can click and drag any planet and watch their relative orbits evolve in time. I was curious ...
0
votes
1answer
63 views

Can the constant $k$ from Kepler's third law be independent of the mass of the planet?

Consider Kepler's third law The square of the orbital period $\tau$ of a planet is directly proportional to the cube of the semi-major axis of its orbit $a$. $\frac{\tau^2}{a^3}=k$ The ...
5
votes
3answers
1k views

How would I calculate celestial body characteristics without a priori knowledge?

Without any a priori knowledge of the mass, speed, distance, and size of local celestial bodies (aside from Earth's size), what can I calculate and how from my "backyard" through observation? Edit: ...
1
vote
0answers
40 views

Semi-major axis , specific mechanical energy, its period and velocity at Apogee and Perigee and what the difference is [closed]

Hi im needing some help with two questions could you please show the formula and the way its solved?Thanks PS:Could you also explain what the difference of velocity and apogee and perigee? 1.)A ...
1
vote
1answer
37 views

Motion under gravitational forces

In a system of particles, can a particle be considered to be attracted to the combined center of mass of the other particles if the Newton's universal law of gravitation is used (the inverse square ...
1
vote
5answers
97 views

How can escape velocity and gravitational potential be higher in weaker gravitational fields?

on Earth we have an escape velocity of about 11180 m/s and a gravitational field of g=9.81 m/s^2. It would seem obvious that the escape velocity was higher for stronger gravitational fields. Often it ...
3
votes
3answers
78 views

Could the Earth-Moon rotation period equal one Earth year?

I just stumbled on this rather confused QA. The point seems to be if the Earth-Moon rotation period was identical to the Earth-year, then ... ... all three would stay in a line at all times. ...
1
vote
0answers
28 views

Orbital period of a satellite in Kerbal Space Program

Let me start off by saying I am really bad at maths and physics, but lately I have been trying to calculate the orbital period of a satellite I have put in orbit around a planet called Kerbin in a ...
1
vote
2answers
88 views

How has the world remained in balance?

In the center of our galaxy, there is a Supermassive black hole. We were told in early astronomy units of school that black holes are giant vacuums that will absorb/consume the area around it. My ...
3
votes
1answer
108 views

Relation between eccentric and true anomalies

If $v$ is the true anomaly and $E$ the eccentric anomaly, how can I show that $$\frac{dv}{dE}=\frac{b}{r}=\frac{\sin v}{\sin E}~?$$
14
votes
4answers
7k views

Can the Earth leave orbit if the population of humans and other live forms increases?

I don't know a lot about physics, but this seemed like the correct place to ask my question. I apologize in advance if it is a ridiculous one. It's actually a two part question: If the population ...
4
votes
1answer
113 views

Why does planetary spin affect the stability of orbits?

Reading about the Hill Sphere I notice that "the region of stability for retrograde orbits at a large distance from the primary, is larger than the region for prograde orbits at a large distance from ...
1
vote
0answers
24 views

Topic on relativistic celestial mechanics [closed]

I have to do a small 10-15 minutes presentation about celestial mechanics, and I am searching for a topic. As a mathematician my background in physics is not very extensive, but I have some notions ...
8
votes
3answers
705 views

Parallax, obliquity, precession, and Orion?

Today, the obliquity of the earth is about 23.4°. 6500 years ago, it was about 24.1° Imagine the blue square is the constellation of Orion, and the yellow star is the sun. Viewpoint B is you, on ...
5
votes
3answers
109 views

Elliptical orbit changing as a star's mass increases

I'm studying Kepler's Laws, specifically the orbit of the Earth around the Sun. I know that if the Earth was more massive, the orbit would not be significantly affected. If the Sun was more massive, I ...
0
votes
0answers
37 views

How to calculate angle between two objects in orbit

So I have 2 objects in orbit around the same body, and I have all the orbital elements associated with each body. How do I calculate the angle between them both or figure out when they are a certain ...
0
votes
1answer
64 views

Why do the stars in a binary system, revolve diametrically opposite to each other?

I encountered this question, as I was reading up on Gravity. The author of my textbook says that the stars orbit a common centre which is their center of mass. I somehow think that this fact might ...
1
vote
0answers
25 views

Laplace's method to determine orbits

I am trying to do the second problem by Laplace's method, it is in spanish but the only thing that matters are the asteroid's observations and the coordinates of Earth https://freeshell.de/~rgh/arch/...
1
vote
1answer
55 views

Can a planet's orbit around a star be simulated? [closed]

Say I know all parameters like density, size, rotational velocity of a planet, could I predict its orbit around a star where I also know parameters of it? I want to design a simple model of the solar ...